The Army Comrades' Association was established in Ireland in February 1932. The organisation soon became known as Blueshirts. In July 1933, Eoin O'Duffy, became leader of the Blueshirts. O'Duffy renamed the movement the National Guard. He also organized marches, flags, salutes ("Hail O'Duffy) based on those in Nazi Germany. This led to fighting in the streets between the National Guard and left-wing groups. In August 1933 the government banned the National Guard from marching to Leinster Lawn.
On the outbreak of the Spanish Civil War O'Duffy began recruiting volunteers to go and fight in the war. Supported by the Catholic Church in Ireland and by right-wing national newspapers, O'Duffy and the first volunteers left travelled from Dublin on 13th November, 1936. It has been argued that the men who went to Spain were mainly motivated by a desire to defend the Catholic Church in Spain.
An estimated 750 Blueshirts fought with the Nationalist Army during the war. The Irish volunteers became part of the XV Bandera Irlandesa del Terico of the Spanish Foreign Legion. The Blueshirts suffered heavy losses at Jarama in February 1937.
On his return to Ireland in 1938 Eoin O'Duffy published his book, Crusade in Spain. O'Duffy continued to advocate fascist policies and during the Second World War he had negotiations with politicians in Germany about the possibility of persuading the Irish Republican Army of undertaking a policy of sabotage against Britain.